Usually, the reproductive act by which sperm cells are transferred from a male to a female. In hummingbirds, the male has no intromittent structure (penis), so copulation consists of a quick touch of the tips of the cloacas of the two mates.

act of fertilization, may be brief or lengthy; male holds female as in tandem, but tip of female's abdomen swings up to contact second segment of male, where accessory genitalia located (sperm transfer already accomplished)

copulatio - sexual coupling] The sexual act of a male and female, of the same species, coming together for the purpose of delivering and receiving sperm respectively. The term can also refer to sexual behavior that enhances the possibility of fertilization.

Copulation is performed by the male which comes behind the female and inserts the penis under the female shell and mantle, up to the copulating pouch. It is possible to observe a male copulating with a spawning female. It does not mean that the eggs are immediately fertilized. The eggs have to be fertilized by sperm well before being coated by jelly coat and protecting envelopes. The male takes the opportunity of a female which does not move much as it is occupied during one day to lay eggs. And the sperm is put in the seminiferous pouch up to next spawning. Copulation is not very selective as it is possible to encounter males trying to copulate with females of a different species or even with another male. A female may be fertilized by two successive males.